1. Field of the Invention
The present invention relates to a magnetic disk unit, and more particularly, to a method of reproducing data and a control device using a dummy read gate for controlling a pulse width, a pulse generating location or the number of pulses, before reading data from a disk.
2. Description of the Related Art
A hard disk drive, one type of computer auxiliary memories, is used for reproducing data from a disk by a magnetic head, or writing new data on the disk by the magnetic head. In order to obtain a hard-disk drive having high-capacity, high-density and of small-size, recording parameters such as BPI (bits per inch), and TPI (tracks per inch) decrease, thereby a method and device for accurately and rapidly controlling a head location are required.
Generally, since a target sector is detected using a reproduction instruction and a read gate is generated in the target sector, a mode set of channel IC for the corresponding target sector is interlocked into the read gate. Thus, a preset mode is difficult to obtain, and AGC (amp gain control), asymmetry control or FIR (finite input response) filtering, etc., do not give sufficient time for a preliminary tuning of a signal of the read gate or post tuning of the signal of the read gate. A dummy read technique is developed for solving the above-described problems. In this technique, a dummy read signal is generated in a data sector prior to the target sector, before the read head reaches the target sector, thus tuning a channel of the read head.
However, while the dummy read signal according to the related art is generated in the data sector prior to the target sector, the pulse width, the pulse generating location or the number of pulses cannot be controlled. This is due to the short distance between a sector, which a head reaches for the first time, and the target sector, or due to a defect sector, existing in a sector performing the dummy read, thus setting an inaccurate channel parameter by erroneous information. Thus, a read error is generated in the target sector and the location for performing the dummy read is erroneous, and the dummy read function cannot be efficiently performed.